Production of high-octane gasolines



Nov. 14, 1961 R. c. HANSFORD ET AL 3,008,895

PRODUCTION oF HIGH-ocmw: GASOLINES Filed Aug. 25. 1959 w W T W@ JW ...my mr M m wm E, 4 af.

wav. W LLB Unit@ This invention relates to a combination of interdependent refining and conversion steps, whereby mineral oil fractions boiling in the gas oil range may be converted into extremely high-quality gasolines at high liquid yields. In broad aspect, the invention comprises subjecting the gas oil feed to catalytic hydrocracking, preferably using as the catalyst a coprecipitated silica-zirconia-titania b-ase promoted With a small amount of a group VIB or group VIII metal, and then subjecting the hydrocracked gasoline to catalytic reforming, preferably under relatively mild conditions. It is found that by using the preferred hydrocracking catalysts, the gasoline produced is an ideal reforming feedstock; it is rich in monocyclic naphthenes, low in fused-ring polycyclics, and low in sulfur. Other hydrocracking catalysts, though operative in the process, are found to be less selective for converting fused-ling aromatics to monocyclic naphthenes, less active in the presence of basic nitrogen, and less active for desulfurization; the resulting gasoline is hence less desirable as a reforming feedstock.

According to a preferred modification of the process, the gas oil feed is rst subjected to catalytic hydrofning to effect partial hydrogenation, desulfurization and/or denitrogenation, and the hydroiined gas oil is then subjected to the hydrocracking and reforming steps. It is found that, by employing the hydrofining step, catalyst life is improved, higher overall gasoline yields are obtained, the gasoline is of superior anti-knock quality, and the overall hydrogen consumption per barrel of gasoline produced is lower.

According to another modification of the process, the hydrocracked gasoline is treated by solvent extraction or selective adsorption to remove aromatiehydrocarbons therefrom, and only the non-aromatic portion is subjected to reforming. Optionally, the small amount of gasoline produced in the hydroning step may also be treated for aromatics removal and then reformed, or it may be sent directly to the reformer along with the hydrocracked gasoline.

The principal advantage of the present combination, aside from the extremely high quality gasoline obtained with minimal hydrogen consumption, is that each of the principal unit operations, i.e., hydrolining, hydrocracking, and reforming, may be conducted under optimum conditions, usually relatively mild, so that very little of the feed is converted'to coke and light gases, and the catalyst life in each processing unit -is greatly extended, all resulting in high liquid yields of gasoline and low catalyst maintenance costs.

Other more general objects of the invention include the following:

(l) To provide a process whereby one of the most unproiitable products in a refinery, namely residual oils from cracking operations, may be converted to one of the most valued and most needed, namely high-quality gasoline having a leaded octane rating in excess of 100;

(2) To provide a process wherein the unit operations are so integrated that this conversion may be effected at liquid yields in excess of 100%, based on the gas oil feed;

(3) To provide conditions such that the hydrocracking, hydroiining and reforming steps may be operated substantially non-regeneratively, i.e. so that the catalysts employed in these operations may be maintained ontates attent O Mice stream for periods of several weeks without requiring regeneration;

(4) To provide specific hydrocracking catalysts and techniques correlated so as to avoid both over-hydrogenation of the feed, and the cracking of monocyclic naphthenes in the processing of aromatic and/or naphthenic oils;

(5) To integrate controlled hydrogenation into a hydrocracking-reforming combination in such a manner as to obtain maximum benefits from the total hydrogen consumed, i.e. to avoid using hydrogen merely to make light paraflins, and to favor its ultimate incorporation into side-chains on monocyclic aromatic hydrocarbons;

(6) To provide a reformer feedstock which may be benefited t-o the optimum extent by mild reforming, involving mainly dehydrogenation and laromatization of naphthenes, and does not require the relatively severe reforming conditions required for effecting dehydrocyolization reactions, or extensive isomerization reactions, in order to achieve the optimum yield-octane relationship.

The foregoing objects, as well as others which will appear hereinafter, are achieved by the methods described herein.

With the advent of modern high compression ratio automotive engines, and the greatly increased consumption of gasoline, the need for extremely high-quality gasoline has become more acute in recent years. Conventional methods for producing super-octane gasolines are by alkylation, and by reforming. Alkylation is an expensive operation, and reforming has definite limitations 'based on available feedstocks. Catalytic reforming, or hydroforming, involves several types of reactions, the principal of which are dehydrogenation of naphthenes to produce aromatics, isomerization of straight-chain paraiiins to branched-chain paraiins, the iso-merization of fve-membered naphthenes to six-membered naphthenes followed by dehydrogenation, and the dehydrocyclization of parains to form aromatics. Only the dehydrogenation reactions can be made to take place under conditions of reforming which do not result in excessive cracking of the stock. Consequently, the value of a reforming operationis limited by the inherent nature of the feedstock; if the stock is low in naphthenes, severe reforming conditions resulting in low liquid yields'must be employed to obtain significant octane improvement. If the same stock is treated under mild conditions merely to elect dehydrogenation, very little Ibenefit is obtained. The principal value of reforming therefore appears when treating feedstocks rich in naphthenes, Wheer the treatment may be performed under mild conditions, thereby obtaining significant octane improvement without excessive loss in liquid yield and coking of the catalyst.

The hydrofining step of this invention is designed to` effect decomposition of a substantial portion of organic sulfur, nitrogen and oxygen compounds, while avoiding any appreciable hydrocracking of hydrocarbons. Any olens present are mostly hydrogenated. The polycyclic aromatic compounds are only partially hydrogenated. Under these conditions, only small amounts of gasoline are produced, nearly all of which consists of hydrocarbon fragments resulting from the splitting out of sulfur, nitrogen and oxygen from heterocyclic compounds. Hydrogen `consumption in this step is usually between about 400 and 2000 s.c.f. per barrel of feed, and constitutes betweenabout 30% and 80% of the'total hydrogen consumption in the hydroning and hydrocracking steps.

`The resulting gas oil is not greatly changed as to total content of acid-solubles, and the aniline point is usually only about 5-20 points higher than the original cycle oil. The quality of the gasoline produced during hydroning :is surprisingly high; its total content of ring compounds 3 (aromatics plus naphthenes) generally runs between about 40% and 90% by volume.

As a result of hydroning, the succeeding hydrocracking step may be carried out under milder conditions, since the major objective becomes primarily one of effecting scission of naphthenic -rings attached to aromatic rings, or aliphatic sideachains attached to aromatic rings. Consequently, high partial pressures of hydrogen, such as would tend to hydrogenate monocyclic aromatic compounds and lead to their ultimate cracking to paraflins, can be avoided. At the same time, monocyclic naphthenic rings are preserved due to the selectivity of hydrocracking conditions, a result which would not be achieved by conventional cracking lin the absence of hydrogen.

The hydroeracking conditions are thus adjusted so as to avoid the complete hydrogenation of polycyclic aromatcs, and also the cracking of monocyclic naphthenes. The resulting gasoline may contain substantially the same total content of ring compounds as did the feed, but a large proportion of the polycyclic aromatics have been converted to monocyclic aromatics, while -a substantial proportion of monocyclic naphthenes are synthesized. It is important to note that under these conditions of selective hydrocracking, the gasoline produced contains almost a cons-tant fraction of ring compounds (aromatics plus naphthenes) over a wide ran-ge of conversions. Thus, the C6+ gasoline fraction may contain 90% of total ring compounds, of which 30-70% may be benzene derivatives, and the remainder n-aphthenes. Under the same hydrocracking conditions, but without the preferred hydrofining treatment, the gasoline would contain only about 'i5-80% total ring com-pounds, of which the total proportion of naphthenes is substantially lower. In any case however, the hydrocracker gasoline of this. invention contains at least 50% by volume of cyclic hydrocarbons and is thus highly desirable for use in catalytic reforming under mild conditions.

The operation of the combined process may be more readily understood with reference to the accompanying flowsheet, illustrating the principal modications, `as applied to the treatment of coker gas oils or cracked gas oils.

The initial charge oil is brought in through line 1, preheated to cracking temperatures in preheater 2 and transferred to cracking or coking unit 3. The term cracking is used herein in its broadest sense, to encompass both catalytic and thermal cracking, as well as coking and visbreaking. In the case of coking, the charge oil is generally a crude oil, reduced crude oil or residuurn, which is'preheated lto e.g. 750-950 F. and then transferred to a coking drum where it is allowed to soak in its own heat for several minutes or hours while volatile products boiling in the gas oil range and below arev continuously removed. Alternatively, iiuidized coking, or contact coking with a moving bed of coke pebbles may be employed.

In the case o-f thermal or catalytic cracking in unit 3, the charge oil is generally a distillate boiling in the gas oil range, i.e. between about 400 and 1,000n F. Either straight-run gas oils and/ or Coker gas oils m-ay be utilized. lf catalytic cracking is employed, any conventional catalysts may be used such as synthetic coprecipitated silicaalumina, silica-zirconia, silica-magnesia, silica-bo-ria, acid-treated montmorillonite clays, e.g. acid-washed bentonites, or the like. Typical catalytic cracking conditions include temperatures of about 850-1050 F., pressures of to 50 p.s.i.g., cat/oil ratios between about 1 and 20, and liquid hourly space velocities ranging between about 0.5 and 20 volumes of liquid feed per volume of catalyst per hour. Thermal cracking generally involves the use of slightly higher temperatures, e.g. 900-l 100 F., pressures of 0l500 p.s.i.g., and residence times ranging between yabout 1 second and 30 minutes, depending upon the temperature.

For best results in the subsequent steps of this process, it is preferred to obtain from unit 3 an oil boiling in the gas oil range which is relatively enriched in fusedning aro-matics, as compared to straight-run gas oils. Cycle oils from the cracking operations, or Coker gas oils, are preferred, conforming to the following specilications:

In place of the foregoing gas oils, all of which are cracked to some extent, it is also contemplated that straight-run gas oils may be used in the subsequent steps of the process, either alone or in adminture with one or more of the cracked oils.

The products from cracking or coking zone 3 are subjected to convention-al distillation steps not shown to produce a gasoline product which may be removed through line 4. The gas oil residue is taken olf through line 6, and is then admixed with recycle hydrogen from line 8 and makeup hydrogen from line 9, and the combined material is then passed through a preheater 10 to raise the stock to hydroiininig temperatures. The preheated stock plus hydrogen is then admitted to hydrofining zone 12.

HYDROFINING STEP In hydroiim'ng zone i2 the feed plus hydrogen is contacted with a suitable sulfactive hydrofming catalyst under conditions of hydroning. The catalyst is preferably disposed in a iixed stationary bed, and may cornprise any of the oxides and/ or suliides of the transitional metals, and especially an oxide or sulfide 'of a group VIII met-al (particularly iron, ycobalt or nickel) mixed with yan oxide or sulfide of a 'group VIB metal (preferably molybdenum or tungsten). Such catalysts may be employed in undiluted form, but preferably are supported on an adsorbent carrier in proportions ranging between about 2% :and 25% by weight. Suitable carriers include in general the diiiicultly reducible inorganic oxides, e.g. alumina, silica, zirconia, titania, clays such as bauxite, bentonite, etc. Preferably the carrier should display lit# tle or no cracking activity, and hence highly acidic carriers are to be avoided. The preferred carrier is activated alumina, and especially activated alumina containing about 3-15 by weight of coprecipitated silica gel.

The preferred hydroiining catalyst consists of cobalt oxide plus molybdenum oxide supported on silica-stabilized alumina. Compositions containing between about 2% and 8% of CoO, 4% and 20% of M003, 3% and 15% of SiO2, and the balance A1203, and wherein the mole-ratio of COO/M003 is between about 0.2 and 4, are speciiically contemplated. These catalysts are preferably prepared by alternate impregnation with aqueous solutions of ammonium molybdate land cobalt nitrate, as described in U.S. Patent No. 2,687,381.

Suitable hydroiining conditions are as follows:

Operative Preferred Average bed temperature, F GOO-850 700-825 Pressure, p.s.i.g 500-5, 000 800-4, 000 Liquid hourly space velocity.. 1-20 2-10 Hydrogen ratio, s.c.f./hbl 500-12, 000 800-8, 000

.as hereinafter described. The hydroner gas oil, boiling within the range of about 375-750 F., is taken otf via line 15, preheated in heater 16, and subjected to hydrocracking in hydrocracking zone 17, after being admixed with hydrogen from line 18, and, optionally, Vith cycle oil from the hydrocracker which is admitted to line 15 via line 19.

Alternatively, Where no hydrofining step is employed, the feed to hydrocracking zone 17 is .the gas oil from line 6. This may be diverted directly to the hydrocracker vi-a lines 6, 7 and 15 by closing valve 13 and opening valve 11.

HYDROCRACKING STEP In hydrocracking zone 17, the charge oil plus hydrogen is contacted with a bed of suitable hydrocracking catalyst under conditions of hydrocracking. The catalyst may consist of a conventional cracking component plus a minor proportion of a heavy met-al oxide or sulfide which is effective in the promotion of hydrogenation reactions. .Such catalysts may comprise for example between about l1% and 10% by weight of the oxides or suldes of the transitional metals, particularly those of groups VB, VIB, VIIB and VIII, or mixtures thereof. Particularly desi-rable components consist of the oxides or suldes of chromium, molybdenum, tungsten, iron, cobalt, nickel, or the metals platinum, or palladium. The carrier on which these materials are deposited may consist for example of synthetic coprecipitated silica-alumina, silica-zirconia, silica-titania, siliea-tatania-zirconia, silica-magnesia, and the like. Acid-activated montmorillonite clays may also be employed. Any of these carriers may be further activated by the incorporation of small amounts of acidic materials such as fluorine or chlorine.

The preferred group of catalysts for the hydrocracking reaction .consists of a coprecipitated base composed of l065% silica, 15-.65% titania, and 15-65% zirconia, on which is deposited as by impregnation or coprecipitation va minor amount, from about 0.5% to about 7%, of a promoter, e.g. lan oxide of chromium7 molybdenum, tungsten, cobalt, nickel, .or any combination thereof. Alternatively, even srnaller proportions, between about 0.05% and 1.0% 0f the metals platinum or palladium may' be employed. The oxides and sulfides or other transitional metals may also be used, but to less advantage than the foregoing. These compositions appear to exhibit an extremely high intrinsic activity for promoting the partial hydrogenation and cracking of high molecular weight aromatics, with but little tendency to cause cracking of monocyclic naphthenes. presence of basic nitrogen, and also excel in desulfurization activity, as compared to other hydrocracking catalysts. The preparation and use of these preferred catalysts is more particularly described in the copending applications of Rowland C. Hansford, Serial Nos. 617,222 and 698,398.

Of the preferred catalysts, those described in Serial No. 698,398 constitute a preferred sub-group, being prepared by .coprecipitating all components of the catalyst simultaneously from aqueous solutions of appropriate salts. Further, the coprecipitation is preferably conducted under prevailingly alkaline conditions, i.e. at a pH between about 6 and l2.

Operative temperatures in the hydrocracking zone ldepend to some extent upon whether the preferred hydroning step is used. In the absence of the pre-hydrotining step, hydrocracking temperatures (average bed) may suitably range between about 750 and l000 F., and preferably between about 800 and 900 F. Where the feed is first subjected to hydrofining, lower hydrocracking temperatures are normally used, between about 650 and 950 F., preferably between about 700 and 900 F.

Pressures in the hydrocracking zone may range between about 300 and 6,000 p.s.i.g., and preferably between about .500 and 5,000 psig. Lower pressures within these They are more active in the ranges may be preferred when the pre-hydrotining step is utilized, e.g. between about 500 and 2,500 p.s.i.g. The liquid hourly space velocity may range between about 0.5 and 8 volumes of liquid feed per volume of catalyst per hour. Suitable hydrogen ratios are from 800 to 15,000 s.c.f./bbl. of feed.

It will be understood that these hydrocracking conditions should be adjusted to meet lthe peculiarity of the specific feedstock which is being treated. For highly aromatic feeds, the conditions should be relatively severe; for feeds which contain substantial proportions of naphthenes, the conditions should be relatively mild.

The products of hydrocracking are then subjected to a conventional fractionating sequence, not shown, to separate the products. The unused hydrogen is recycled via lines 20 and 18, and the gasoline fraction boiling between about 250" and 450 F. is taken off via line 21 for subsequent reforming as hereinafter described. The gasoline boiling up to about 200 F. (C4-C6 fraction) is preferably not subjected to reforming, but is separated from the heavy naphtha for any desired subsequent use. The hydrocracking residue, boiling above about 400 F., is .taken off through .line 22, and is recycled to hydrocracking zone 17 via line 19, or to hydrotining .zone 12 via lines 23 and 32, or to the initial cracking step 3 via lines 23 and 29. Alternatively, a part ofthe hydrocracking cycle oil may be recycled to the hydrocracking zone, and the remainder recycled to the initial cracking step and/ or the hydroner. The choice among these alternatives depends upon the specific nature of the charge stock to the hydrocracking zone, and the specic condi-tions of hydrocracking. and the type of cracking carried out in zone 3. Where the cracking in zone 3 is coking, or thermal .cracking, it -is .preferred not to recycle any of the hydrocracking residue thereto, but to recycle all of it back to` the hydrocracking zone and/or the hydroiining Zone. Where catalytic cracking is employed `in zone 3, and the conditions of hvdrocracking in zone 17 are so mild that the residual oil therefrom contains an appreciable lquantity of partially naphthenie polycyclic compounds it is pre- Iferred to recycle most or all of the stock to the catalytic cracking zone. Conversely, when the conditions of hydrocracking are relativelyI severe, whereby the residual .oil therefrom is low in naphthenic compounds, lit is preferred to recycle entirely to the hydrocracking zone and/ or the hydrotining zone. When using the preferred silicazirconia-titania catalyst promoted by other hydrogenating metals or .metal oxides, it is preferred to recycle the stock substantially exclusively back to the hydrocracking zone. With any of these systems of recycle, it is found that the cycle stock from hydrocracking may be recycled to extinc- .tion if desired, without undue coking of the catalyst in anv of the contacting zones.

The consumption of hydrogen in hydrocracking zone 17 is appreciable, usually ranging between 1about 300 and 1500 scf. per barrel of feed. Occasionally, higher or lower hydrogen consumption figures maybe encountered. In any case. however, the hydrogen consumption is less when the hvdrotining step is utilized, and the over-all hydrogen consumption in both steps is about 20-30% less per barrel of total gasoline product at comparable .quality levels, than could be .obtained bv hydrocracking alone. Normally` about 35% .to 70% of the feed is converted to gasoline-boiling-range material in each pass through the hvdrocracker.

The gasoline produced by hvdrocracking in zone 17 is substantially equal in octane rating to the gasoline produced by catalytic cracking in zone 3. However, in distinction to the zone 3 gasoline, the zone 17 gasoline is capable of still greater and substantial improvement by catalytic reforming, due to its much higher content of naphthenes. This gasoline is hence treated by mild reforming, either in toto, or following removal of the aromatic component. IfV the gasoline is to be treated directly,- it is transferred via line 21 and preheater 25 to reforming zone 26, after being admixed with recycle hydrogen admitted via line 27.

SOLVENT EXTRACTlON Where the aromatic content is particularly high, it may desirable to divert the hydrocracker gasoline through line 28 to solvent extraction column 30, wherein the gasoline contacts a suitable solvent which is selective for aromatic hydrocarbons. Suitable solvents include for example ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, or mixtures thereof with methanol, ethanol, or propanol, propionitrile, beta,betaoxydipropionitrile, beta, beta-thiodipropionitrile and the like. Alternatively, extractive distillation may be employed using solvents such as phenol, aniline, benzonitrile, nitrobenzene, methyl cellosolve, ethyl cellosolve and the like. An even more selective separation method consists of Selective adsorption on silica gel or other suitable adsorbents. Any method for effecting either a rough or a complete separation of aromatics from non-aromatics may be employed. These pro- Cedures are conventional and need not be described in detail.

Where solvent extraction is employed, the non-aromatic rainate is recovered from the top of column 30, and sent via line 31 and preheater 25 to reforming zone 26. The aromatic extract, is withdrawn through line 33 and transferred to a solvent recovery zone 34 wherein solvent is recovered by conventional methods such as distillation, and recycled to the extraction column via line 35. The aromatic gasoline fraction recovered in zone 34 is then withdrawn via line 36, and may be used in any desired manner, as e.g. blending with the final reformer gasoline.

The hydroner gasoline may be treated in the same manner as the hydrocracker gasoline, i.e. either reformed directly, or following solvent extraction. Both gasolines are good reforming stocks by virtue of their high naphthene content. To reform both stocks directly, valves 37 and 38 are closed, and valves 39 and 40 opened, whereby the hydrofiner gasoline ows through lines 14 and 41 into line 21, where it joins the hydrocracker gasoline. To effect solvent extraction of both stocks, valves 39 and 40 are closed and valves 37 and 38 opened, whereby both stocks flow into line 28. To reform the hydroner gasoline directly, and solvent extract only the hydrocracker gasoline, valves 38 and 40 are closed, and valves 37 and 39 opened, the former then flowing through lines 14, 41 and 21, and the latter through lines 21 and 2S. To reform the hydrocracker gasoline directly, and solvent extract only the hydroner gasoline, valves 37 and 39 are closed and Valves 38 and 40 opened, whereby the former flows directly to the reformer via line 21, and the latter flows to solvent extractor 30 via lines 14 and 28. The choice of these four alternatives depends mainly upon the aromatic content of the respective gasoline; solvent extraction is generally preferred for gasolines containing more than about 30-40% aromatics, this figure obviously being variable depending upon prevailing economics.

REFORMING STEP ln reforming zone 26 the charge is subjected to mild reforming conditions adapted to convert the major portion of the naphthenes to aromatics. Such conditions comprise: average bed temperatures between about 825- 950 F., space velocities between about 1.5 and 5.0, pressures between about 200 and 800 p.s.i.g., and hydrogen rates between about 4,000 and 12,000 s.c.f. per barrel of feed. The preferred temperatures are between about 85 0 and 925 F., at preferred space velocities of 2-4. Conventional hydroforming conditions include space velocities of about 2 at temperatures of 925 -975 F. These conditions are unnecessary herein and may cause a reduction in liquid yield uncompensated by any sucient increase in gasoline quality.

While the above conditions of reforming are preferred, the more conventional temperatures (925 975 F.) may also be employed. The character of the feed is such that severe reforming conditions, such as would cause substantial reduction in yield when using conventional feeds, do not unduly impair the present liquid yields. This refleets the low paraffin content of the feed, which is the major contributor of light cracked products.

The catalyst employed in reforming zone 26 may be conventional. For example, composites of activated alumina with minor proportions of platinum, palladium, molybdenum oxide, vanadium oxide, or chromium oxide may be employed. The preferred catalysts comprise activated alumina containing minor proportions of fluorine, and minor proportions, from about 0.05% to 1.0%, of platinum. Platinum supported on steam-deactivated silica, or silica-alumina may also be employed. These catalysts are conventional in the art and hence need not be described in detail.

Another type of reforming catalyst which may be used to advantage consists of cobalt molybdate supported on activated alumina, bauxite, or other clays. Such catalysts generally contain between about 2% and 8% by weight of COC, and between about 4% and 20% of M003. Preferably they are prepared by alternate impregnation as described in U.S. Patent No. 2,687,381.

The reforming product is then subjected to conventional separation techniques not shown, to recover a hydrogen recycle stream in line 43. Since the reforming step results in a net make of hydrogen, only a part thereof is recycled to the reforming step via line 27, the remainder being cycled via lines 43 and 18 to hydrocracking zone 17, and/or via lines 43, 9 and 8 to hydroiining zone 12. lf desired, a conventional hydrogen purification step, not shown, may be employed to reduce the concentration of light hydrocarbons in the recycle gas streams. Makeup hydrogen is supplied to hydroning zone 12 via lines 47 and 48, and to hydrocracking zone 17 via lines 47 and 49. The gasoline from reforming zone 26 is then withdrawn via line 45, and sent to storage, not shown, and is found to be of exceptionally high quality. Its aromatic content typically ranges between about 70% and 90% by volume, and its octane rating (F-1-l-3 ml. TEL) typically ranges between about 103 and 108. The gasoline recovered from solvent recovery zone 34 may be even higher in quality. Both of these materials hence provide excellent blending stocks.

The process is more specifically illustrated in the following examples, which should not however be construed as limiting in scope.

Example I Several experiments were carried out to determine tne relative desulfuriza-tion activities and hydrocracking activities of a conventional nickel oxide on silica-alumina catalyst, and t-wo representative hydrocr'acking catalysts of this invention. The respective catalysts were as fol- Each of the `above catalysts was then tested 4for hydro cracking ya cycle oil from a catalytic cracking plant, the hydrocracking conditions and inspection data of the cycle oil being as follows:

Cycle Oil Hydrocraeking Conditions Gravity API 23.7 Temp., F 850 Boiling Range, F 438-657 Pressure, p.s.i.g 3,000 Sulfur, wt. percent 1. 26 2 Nitrogen, wt. percent 0. 134 H2, s.c.f./bbl 8,000

9 Analysis of rthe respective hydrocracked products showed -that catalysts 2 Iand 3 were more active for hydrocracking than catalyst 1, giving significantly higher gasoline yields. The sulfur and nitrogen contents of the hydrocracked gasoline and the uncracked residual oil were as follows:

Gasoline Residual Oil, S, Catalyst No. Wt. per- S, Wt. N, Wt. cent percent percent A light catalytic cycle oil (18 API gravity and 650 F. end point) was hydrocracked over a 20% SiO2-50% ZrO2-30% TiO2 catalyst promoted with 1.2% nickel at 850 F., 3000 p.s.i.g., 2.0 LHSV, and 8000 s.c.f. HZ/'bbL of feed. Approximately 50% of the cycle oil was converted in one pass rto a C4+ gasoline having an octane number (Fll3 ml. TEL) of 98.0. The C-lfraction of this gasoline (120-400 F.) contained 49% aromatics, 31% naphthenes, and 20% parains (mostly isoparafins).

The C-tfraction of hydrocracked gasoline was reformed over a commercial 0.4% platinum-alumina reforming catalyst at 880 F., 400 p.s.i.g., 3.0 LHSV, and 8,000 s.c.f. HZ/ bbl. 'Ihe liquid yield of reformate was 97% and it had the following octane values:

Example III A hydrocracked gasoline was obtained by processing a feed blend comprising 45% of unconverted oil from the hydrocracking s-tep :of Example II and 55% of fresh catalytic cycle oil. The catalyst contained twice as much nickel as did the catalyst of Example Il, but the processing conditions were otherwise the same. Approximately 55% of the feed was converted to a C4-lgasoline having an octane number of 92 (F-1-l-3 ml. TEL). The CG-lfraction was found to contain 38% aromatics, 42% naphthenes, and 20% paraflius.

The gasoline was -dehexanized and then reformed over the same 0.4% Pt-alumina catalyst used in Example I. Processing conditions were the same, except that a temperature of 900 F. was employed. Approximately 96% yield of reformate wa-s obtained having the following octane values:

F-1 clear 100.5 F41-1-3 ml. TEL 104.6

When the C4-C6 cut from the dehexanizing step was blended back with the reformate, the blend had the following octane values:

F-l clear F-1-l-3 ml. TFT

10 tions produces equivalent super-octane gasolnes in high yields.

Example III shows moreover that recycling the hydrocracker cycle oil back to the hydrocr-acking step resul-ts in even higher yields of gasoline than where fresh feed is employed exclusively. Hence, the feasibility of recycling to extinction is clearly indicated.

Example IV Another catalytic cracking cycle oil was employed in a series of experiments to test the relative merits of lthe hydroning-hydrocracking-reforming combination versus the hydrocracking-reforming combination. The cycle oil had the following characteristics:

Gravity, API 17.9 Acid solubles, vol. percent 69 Boiling range, F 440-660 Wt. percent sulfur 1.39 Wt. percent nitrogen 0.15

A. Hydrocrackng-reformng.-A portion of this cycle oil lwas first hydrocracked over a coprecipitated 20% SiO2-50% ZrO2-30% TiOZ catalyst which was impregnated with 1.2% nickel. The lhydrocr-acking conditions were as follows:

Temperature, Pressure, ps i g LHSV 2.0 Hz/barrel, s.c.f 800 Under these conditions 53% by volume of C4400 F. gasolinebased on feed was produced, -at a conversion of 43% per pass. The gasoline had an octane number of 98.2 (Fl-{3 ml. TEL). The depentanized gasoline fraction contained 48% `aromatics, 29% naphthenes, and 23% isoparatins by volume.

'The hydrocr-acked gasoline was -then dehexanized and reformed over a commercial 0.4% platinum-on-alumina reforming catalyst at 900 F., 400 p.s.i.g., 3.0 LHSV, and with 8000 s.c.f. H2 recycle/barrel. The yield of reformate was 96.5% by volume -based on dehexanized feed, and the octane number was 100.5 (F-l clear) or 104.6 (F-1-|3 ml. TEL).

B. Hydrojninghydrocrackng-reforming-Another pomtion of the unrefined cycle oil feed was first subjected lowing properties:

Gravity, API 22.4 Acid solubles, vol. percent 63 Aniline pt., C 29.0 Boiling range, F 460-630 Percent sul-fur 0.09 Percent nitrogen 0.05

The gasoline produced during hydroiining contained about 55% aromatics and 30% naphthenes, and had an The hydrotined cycle oil was then hydrocracked under the same conditions as were used for hydrocracking and unrened oil in part A of this example. The conversion was 59%, and 68% by volume of C4-400" F. gasoline was produced per pass, based on feed. The gasoline had an octane number of 98.7 (F-1-l-3 ml. TEL). The C-lfraction of gasoline contained 46% aromatics, 42% naphthenes, and 12% isoparaflins.

Thus, the gasoline produced by hydrocracking the hydrolined cycle oil is not only higher in octane number than that produced from the unreiined cycle oil, but it contains more naphthenes. It is therefore a better stock for subsequent catalytic reforming.

The hydroned and hydrocracked gasoline was then dehexanized and reformed under the same conditions given in part A of this example. The yield of reformate was greater than 95% based on feed, and the octane number (F-l-l-S ml. TEL) was above 105.

ln part A of this example, 2700 s.c.f. of hydrogen was consumed per barrel of C4400 F. hydrocracker gasoline produced. In part B, a total of 2020 s.c.f. of hydrogen was consumed per barrel of total C4-400 F. produced in the hydr-ofining and hydrocracking steps. Thus, the hydroiining-hydrocracking combination uses only about 75% as much hydrogen per barrel of gasoline produced, as the hydrocracking step alone. The increased efliciency of hydrogen utilization is obvious.

Moreover, the residual oil from the hydrocracking step in part B had a higher A.P.I. gravity than the residual oil from part A, clearly indicating superior recycle quality. On a total recycle basis, the eciency of hydrogen utilization is even more markedly improved where the hydroiining step is employed.

in the reforming step of part A, only about 600 -s.c.f. of hydrogen was produced per barrel of dehexanized feed, while in the reforming step of part B, 850 scf. o-f hydrogen was produced. The increased recovery of hydrogen inthe part B reforming step, plus the much lower hydrogen consumption in the hydrocracking step, makes the hydrolining step very attractive economically. In addition, a higher octane potential is provided by incorporating the hydroiining ste-p.

Example V When the hydroning-hydrocracking procedure of Example 1VB is repeated, using as the hydrocracking catalyst an 88% SiO2-12% A1203 carrier impregnated with 5% by weight of M003, a lower conversion i-s obtained, and the gasoline is lower in naphthene content. However, the results are still substantially superior as to yield, gasoline quality, and hydrogen utilization, as compared to hydrocracking the raw cycle oil.

The foregoing examples clearly demonstrate the utility of the process for producing high quality gasoline under conditions which also give high yields and a highly desirable product distribution.

This application is a continuation-in-part of application Serial Nos. 629,339, now abandoned, and 640,719, now abandoned, vfiled December 19, 1956, and February 18, 1957, respectively.

The foregoing description of specic methods and materials for use in this invention is not intended to be limiting in scope except Where indicated. Many variations will occur to those skilled in the art and all such variations which yield essentially the same result are intended to be included. The true scope of the invention is intended to be embraced with the following claims:

We claim:

1. A process for converting a virgin gas oil contaminated with sulfur compounds into high octane gasoline, which comprises first subjecting said gas oil to a cracking step to produce a cracked gasoline and a gas oil rich in fused-ring aromatic hydrocarbons, subjecting said gas oil to hydrocracking in the presence of added hydrogen and a hydrocracking catalyst under hydrocracking conditions including a pressure in excess of 500 p.s.i.g., effective to give a substantial yield of a low-sulfur gasoline rich in monocyelic naphthenes, then without further desulfurization, subjecting at least the non-aromatic portion of the gasoline from said hydrocracking to a mild reforming operation in the presence of added hydrogen and a platinum-containing reforming catalyst, the conditions of reforming including temperatures between about 800- 925 F., liquid hourly space velocities between about 1.5 and 5.0, and pressures between about 200 and 800 p.s.i.g., whereby a high octane gasoline is produced essentially by dehydrogenation of naphthenes, said hydrocracking catalyst -consistinr essentially of a coprecipitated silicatitania-zirconia base and distributed thereon a minor proportion of a transitional metal hydrogenating component.

2. A process as defined in claim 1 wherein the residual oil from said hydrocracking step is recycled at least in part to said cracking step, and wherein said cracking step is catalytic cracking.

3. A process as dened in claim l wherein the residual oil from said hydrocracking step is recycled at least in part to said hydrocracking step.

4. A process as defined in claim l wherein said cracking step is thermal coking.

5. A process as defined in claim 1 wherein said hydrocracking catalyst is composed of a coprecipitated base consisting of 10-65% silica, 1565% titan-ia and 1565% zirconia, and impregnated thereon a minor porportion, between about 0.5% and 7% of a hydrogenating component selected from the group consisting of the metals platinum and palladium, and the oxides of chromium, molybdenum, tungsten, cobalt and nickel.

6. A pnocess for producing high octane gasoline from a virgin gas oil contaminated with sulfur compounds, which comprises first subjecting said gas oil to catalytic cracking in the presence of a siliceous cracking catalyst under conditions of cracking adjusted to produce a high-octane cracked gasoline, and a residual cracked oil boiling between about 400 and 750 F., and containing at least about 25% by volume of acid-soluble components, subjecting said residual oil to hydrocracking in the presence of added hydrogen and a hydrocracking catalyst, maintaining hydrocracking conditions including temperatures between about 750 and 1,000 F., pressures between about 500 and 5,000 p.s.i.g., space velocities between about 0.5 and 8.0, and hydrogen ratios between about 800 and 15,000 scf. per barrel of feed, thereby producing a low-sulfur aromatic-naphthenic gasoline fraction containing substantial proportions of monocyclic naphthenes but containing not more than about 50% by volume of openchain hydrocarbons, separating at least the major portion of the aromatic components from said hydrocracker gasoline thereby producing an aromatic gasoline fraction and a naphthenic gasoline fraction, subjecting said naphthenic gasoline fraction, without further desulfurization, to mild catalytic reforming in the presence of added hydrogen and a platinum-containing reforming catalyst, the conditions of refonming including temperatures of S25-950 F., liquid hourlyA space velocities between about 1.5 and 5.0, and pressures between about 200 and 800 p.s.i.g., whereby a high octance gasoline is produced essentially by dehydrogenation of naphthenes, said hydrocracking catalyst consisting essentially of a coprecipitated silica-titania-zirconia base and distributed thereon a minor proportion of a transitional metal hydrogenating component.

7. A process as defined in claim 6 wherein said hydrocracking catalyst is composed of a coprecipitated base consisting of 10-65% silica, 15-65% titania and 15-65% zirconia, and impregnated thereon a minor proportion, between about 0.5% and 7% of a hydrogenating component selected from the group consisting of the metals platinum and palladium, and the oxide of chromium, molybdenum, tugnsten, cobalt and nickel.

8. A process as defined in claim 6 wherein said hydrocracking catalyst is composed of a coprecipitated base consisting of 10-65% silica, 15-65% titania and 15-65% zirconia, and impregnated :thereon a minor proportion, between about 0.5% and 7% of a hydrogenating component selected from the group consisting of the metals platinum and palladium, and the oxides of chromium, molybdenum, tungsten, cobalt and nickel, and wherein the residual yoil from Said hydrocracking step which boils above the gasoline range is recycled substantially wholly to said hydrocracking step.

9. A process for producing high octane gasoline from a virgin gas oil contaminated with sulfur compounds, which comprises first subjecting said gas oil to catalytic cracking in the presence of a siliceous cracking catalyst under conditions of cracking adjusted to produce a high-octane cracked gasoline, and a residual oil boiling between about 400 and 750 F., and containing at least about 25% by volume of acid-soluble components, subjecting said residual oil to hydrocracking in the presence of added hydrogen and a hydrocracking catalyst, maintaining hydrocracking conditions including temperatures between about 750 and l,000 F., pressures between about 500 and 5,000 p.s.i.g., space velocities betweeny about 0.5 and 8.0, and hydrogen ratios between about 800 and 15,000 s.c.f. per barrel of feed, thereby producing a low-sulfur, aromatic-naphthenic gasoline fraction containing substantial proportions of monocyclic naphthenes but containing not more than about 50% by volume of open-chain hydrocarbons, then, without further desulfurization, subjecting the gasoline from said hydrocracking t a miid reforming in the presence of added hydrogen and a platinumcontaining reforming catalyst, the conditions of reforming including temperatures between about 825 950 F., liqnid hourly space velocities between about 1.5 and 5.0, and pressures between about 200 and 800 p.s.i.g., whereby a high octane gasoline is produced essentially by dehydrogenation of naphthenes, said hydrocracking catalyst consisting essentially of a coprecipitated silica-titania-zirconia base and distributed thereon a minor proportion of a transitional metal hydrogenating component.

l0. A process as defined in claim 9 wherein said hydrocracking catalyst is composed of a coprecipitated base consisting of 65% silica, 15-65% titania and 15-65% zirconia, and impregnated thereon a minor propoition, between labout 0.5% and 7% of a hydrogenating component selected fnom the group consisting of the metals platinum and palladium, and the oxides of chromium, molybdenum, tungsten, cobalt and nickel.

l1. A process as defined in claim 9 wherein said hydrocracking catalyst is composed of a coprecipitated base consisting of 1065% silica, 15-65% titania and 1565% zirconia, and impregnated thereon a minor proportion, between about 0.5% and 7% of a hydrogenating cornponent selected from the group consisting of the metals platinum and palladium, and the oxides of chromium, molybdenum, tungsten, cobalt and nickel, and wherein the residual oil from said hydrocracking step which boils above the gasoline range is recycled substantially Wholly to said hydrocracking step.

12. A process for producing high-octane gasoline from a'mineral oil feedstock boiling in the gas oil range, which comprises subjecting said feedstock to hydrofining in the r presence of a hydrofining catalyst comprising a diicultly reducible adsorbent oxide carrier and supported thereon a minor proportion of a component selected from the class consisting of cobalt oXide-plus-molybdenum oxide and cobalt sullide-plus-molybdenum sulfide, maintaining hydroiining conditions including temperatures between about 600 and 850 F., pressures between about 500 and 5,000 p.s.i.g., space velocities between about l and 20, and hydrogen rates between about 500 and 12,000 s.c.f. per barrel of feed, thereby producing a substantially desulfurized hydrofiner gas oil and a minor proportion of desulfurized hydroner gasoline, subjecting said hydrofiner gas oil to hydrocracking in the presence of a hydrocracking catalyst consisting essentially of a coprecipitated silica-titania-zirconia base and deposited thereon a minor proportion of `a transitional metal hydrogenating component, maintaining hydrocracking conditions including temperatures between about 650.and 950'l F., pressures between about 500 and 5,000 p.s.i.g., space velocities between about 0.5 and 8.0, and hydrogen ratios between about 800 and 15,00 s.c.f. per barrel of feed, thereby producing a high-octane gasoline fraction containing substantial proportions of monocyclic aromatics and naphthenes.

13. A process as defined in claim 12 wherein said feed- 14 stock is a cracked residual oil derived from a catalytic cracking operation.

14. A process as defined in claim 12 wherein said feedstock is a cracked residual oil derived from a coking operation.

15. A process for producing high-octane gasoline from a mineral oil feedstock boiling in the gas oil range, which comprises subjecting said feedstock to hydrofining in the presence of hydrogen and a hydrofining catalyst, thereby producing a substantially desulfurized hydroner gas oil and a minor proportion of desulfurized hydrofiner gasoline, subjecting said hydroliner gas oil to hydrocracking in the presence of a hydrocracking catalyst consisting essentially of a coprecipitated silica-titania-zirconia base and deposited thereon a minor proportion of a transitional metal hydrogenating component, maintaining hydrocracking conditions including temperatures between about 650 and 950 F., pressures between about 500 and 5,000 p.s.i.g., space velocities between about 0.5 and 8.0, and hydrogen ratios between about 800 and 15,000 s.c.f. per barrel of feed, thereby producing a hydrocracker gasoline containing substantial proportions of monocyclic aromatics and naphthenes, then subjecting said hydrocracker gasoline to a mild reforming operation in the presence of added hydrogen and a reforming catalyst, the conditions of reforming including temperatures between about 825 and 950 F., a space velocity between about 1.5 and 5.0, and pressures between about 200 and 800 p.s.i.g., whereby a high-octane gasoline is produced essentially by dehydrogenation of naphthenes,

16. A process as defined in claim 15 wherein the residual oil from said hydrocracking step which boils above the gasoline range is recycled substantially wholly to said hydrocracking step.v

17. A process as defined in claim 15 wherein said hydrofiner gasoline is blended with said hydrocracker gasoline, and the mixture is then subjected to said reforming operation.

18. A process as defined in claim 15 wherein said feedstock is a cracked residual oil derived from a catalytic cracking operation.

19. A process as defined in claim 15 wherein said feedstock is a cracked residual oil derived from a coking operation.

20. A process for producing high-octane gasoline from a mineral oil feedstock boiling in the gas oil range, which comprises subjecting said feedstock to hydrolining in the presence of a hydrofining catalyst comprising a difficultly reducible adsorbent oxide carrier and supported thereon a minor proportion of a component selected from the class consisting of cobalt oXide-plus-molybdenum oxide and cobalt sulfide-plus-molybdenum sulfide, maintaining hydrofining conditions including temperatures between about 600 and 850 F., pressures between about 500 Vand 5,000 psig., space velocities between about 1 and 20, and hydrogen rates between about 500 and 12,000 s.c.f. per barrel of feed, thereby producing a substantially desulfurized hydrofiner gas oil and a minor proportion of desulfurized hydrofiner gasoline, subjecting said hydrofiner gas oil to hydrocracking in the presence of a hydrocracking catalyst consisting essentially of a coprecipitated silica-titania-zirconia base and deposited thereon a minor proportion of a transitional metal hydrogenating component, maintaining hydrocracking conditions including temperatures between about 650 and 950 F., pressures between about 300 and 6,000 p.s.i.g., space velocities between about 0.5 and 8.0, and hydrogen ratios between about 800 and 15,000 s.c.f. per barrel of feed, thereby producing a hydrocracker gasoline containing substantial proportions of monocyclic aromatics and naphthenes, separating at least the major portion of the aromatic components from said hydrocracker gasoline thereby producing an aromatic gasoline fraction and a naphthenic gasoline fraction, then subjecting said naphthenic gasoline fraction to mild catalytic reforming in the abbassa i presence of added hydrogen and a reforming catalyst, the conditions of reforming including temperatures of 825- 950 F., liquid hourly space velocities between about 1.5 and 5.0, and pressures between about 200 and 800 p.s.i.g., whereby a high-octane gasoline is produced essentially by dehydrogenation of naphthenes.

Zl. A process as defined in claim wherein the residual oil from said hydrocracking step which boils above the gasoline range is recycled substantially wholly to said hydrocracking step.

' 22. A process as defined in claim 20 wherein said hydro-finer gasoline is blended with said hydrocracker gasoline, and the mixture is then treated by aromatics separation and lreforming as specified in said claim.

23. A process as defined in claim 20 wherein said feedstock is a cracked residual oil derived from a catalytic cracking operation.

24. A process as defined in claim 20 wherein said feedstock is a cracked residual oil derived from a coking operation.

25. A process as defined in claim l5 wherein said hydrofining catalyst comprises a diiiicultly reducible adsorbent oxide carrier and supported thereon a minor proportion of a component selected from the class consisting of cobalt oxide-plus-molybdenum oxide and cobalt sulfide-plus-molybdenum sulfide.

26. In a catalytic refining and conversion system wherein a relatively high-boiling mineral oil feedstock is first subjected to a catalytic hydrofining treatment to effect a partial hydrogenation and desulfurization thereof, without substantial cracking, and the hydrofined feed is then subjected to catalytic hydrocracking at a temperature between about 650 and 950 F., a pressure between about 500 and 5,000 p.s.i.g., a space veiocity between about 0.5 and 8.0, and hydrogen rates between about 800 and 15,000 s.c.f. per barrel of feed, to thereby effect a conversion to relatively low-boiling hydrocarbons, the improvement which comprises utilizing in said hydrocraoking step a catalyst consisting essentially of a coprecipitated silica-zirconia-titania base containing l0- 65% Si02, 15-55% Ti02 and i5-6\5% ZrOZ, and deposited thereon a minor proportion of a transitional metal hydrogenating component, the metal of said hydrogenating component being selected from the class consisting of group VIB and group VIII metals.

27. A process for producing high-octane gasoline from a mineral oil feedstock rich in polycyclic hydrocarbons, said feedstock boiling substantially entirely between about `400" and 750 F., and containing at least about 25% by volume of acid-soluble components, which comprises subjecting said feedstock to hydrolining in the presence of a hydroiining catalyst, maintaining hydrofining conditions including temperatures between about 600 and `825 F., pressures between about 500 and 5,000 p.s.i.g., space velocities between about l and 20, and hydrogen rates between about 500 and 8,000 s.c.f. per bar-rel of feed, and correlating said hydrofining conditions so as to maintain a hydrogen consumption therein between about 400 and 2,000 s.c.f. per barrel of feed, thereby producing'a substantially desulfurized hydro-finer -gas oil and a minor proportion of desulfurized hydroiiner gasoline, subjecting said hydrofiner gas oil to hydrocracking in the presence of a hydrocracking catalyst, maintaining hydrocracking conditions including temperatures between about 750 and 900 F., pressures between about 500 and 5,000 p.s.i.g., space velocities between about 0.5 and 8.0, and hydrogen ratios between about 800 and 15,000 s.c.f. per barrel of feed, thereby producing a hydrocracker gasoline containing substantial proportions of monocyclic aromatics and naphthenes, then subjecting said hydrocracker gasoline to a mild reforming operation in the presence of added hydrogen and a reforming catalyst, the conditions of reforming including temperatures between about 825 and 950 F., liquid hourly space velocities between about 1.5 and 5.0, and pressures bel0 tween about 200 and 800 p.s.i.g., whereby a high-octane gasoline is produced essentially by dehydrogenation of naphthenes.

28. A process as defined in claim 27 wherein said hydrofiner gasoline is blended with said hydrocracker gasoline, and the mixture is then subjected to said reforming operation.

29A A process as defined in claim 27 wherein said feedstock is a cracked residual oil derived from a catalytic cracking operation.

30. A process as defined in claim 27 wherein said feedstock is a cracked residual oil derived from a thermal cracking operation.

31. A process for producing high-octane gasoline from a mineral oil feedstock rich in polycyclic hydrocarbons, said feedstock boiling substantially entirely between about 400 and 750 F, and containing at least about 25% by volume of acid-soluble components, which comprises subjecting said feedstock to hydrofining in the presence of a hydrofining catalyst, maintaining hydrofining conditions including temperatures between aboutr 600 and 825 F., pressures between about 500 and 5,000 p.s.i.g., space velocities between about l and 20, and hydrogen rates between about 500 and 8,000 s.c.f. per barrel of feed, and correlating said hydrofining conditions so as to maintain a hydrogen consumption therein between about 400 and 2,000 s.c.f. per barrel of feed, thereby producing a substantially desulfurized hydroner gas oil and a minor proportion of desulfurized hydrofiner gasoline, subjecting said hydrofiner gas oil to hydrocracking in the presence of a hydrocracking catalyst, maintaining hydrocracking conditions including temperatures between about 750 and 900 F., pressures between about 500 and 5,000 p.s.i.g., space velocities between about 0.5 and 8.0, and hydrogen ratios between about 800 and 15,000 s.c.f. per barrel of feed, thereby producing a hydrocracker gasoline containing substantial proportions of monocyclic aromatics and naphthenes, separating at least the major portion of the aromatic components from said hydrocracker gasoline thereby producing an aromatic gasoline fraction and a naphthenic gasoline fraction, subjecting said naphthenic gasoline fraction to mild catalytic reforming in the presence of added hydrogen and a reforming catalyst, the conditions of reforming including temperatures of 825-950 F., liquid hourly space velocities between about 1.5 and 5.0, and pressures between about 200 and 800 p.s.i.g., whereby a high-octane gasoline is produced essentially by dehydrogenation of naphthenes.

32. A process as defined in claim 31 wherein said feedstock is a cracked residual oil derived from a catalytic cracking operation.

33. A process as defined in claim 3l wherein said feedstock is a cracked residual oil derived from a thermal cracking operation.

34. A process for producing high-octane gasoline from a mineral oil feedstock boiling above the gasoline rang which comprises subjecting said feedstock to non-hydrogenative cracking to produce a cracked gasoline and a cracked gas oil, said cracked lgas oil boiling substantially entirely between about 400 and 750 F., and containing at least about 25% by volume of acid-soluble components including a substantial proportion of polycyclic aromatic hydrocarbons, subjecting said cracked gas oil to hydrofining in the presence of a hydrofining catalyst, maintaining hydrofining conditions including temperatures between about 600 and 825 F., pressures between about 500 and 5,000 p.s.i.g., space velocities between about l and 20, and hydrogen rates between about 500 and 8,000 s.c.f. per barrel of feed and correlating said hydrofining conditions so as to maintain a hydrogen consumption therein between about 400 and 2,000 s.c.f. per barrel of feed, thereby producing a substantially desulfurized hydrofiner gas oil and a minor proportion of desulfurized hydroiiner gasoline, subjecting said hydroliner gas oil to hydrocracking in the presence of a hydrocracking catalyst, maintaining hydrocracking conditions including temperatures between about 750 and 900 F., pressures between about 500 and 5,000 psig., space velocities between about 0.5 and 8.0, and hydrogen ratios between about 800 and 15,00 s.c.f. per barrel of feed, thereby producing a hydrocracker gasoline containing substantial proportions of monocyclic aromatics and naphthenes, then subjecting said hydrocracker |gasoline to a mild reforming operation in the presence of added hydrogen and a reforming catalyst, the conditions of reforming including temperatures between about 825 and 950 F., liquid hourly space 'velocities between about 1.5 and 5.0, and pressures between about 200 and 800 p.s.i.g., whereby a high-octane gasoline is produced essentially by dehydrogenation of naphthenes.

35. A process as dened in claim 27 wherein said hydrocracking conditions are correlated so as to maintain a hydrogen consumption in the hydrocracking step of between about 300 and 1,500 s.c.f. per barrel of feed.

36. A process as dened in claim 27 wherein the unconvented oil boiling above the @gasoline range from said Ihydrocracking step is recycled at least in part to said hydrocracking step.

37. A process as dened in claim 31 wherein said hydrocracking conditions are correlated so as to maintain a hydrogen consumption in the hydrocracking step of between about 300 and 1,500 s.c.-f. per -barrel of feed.

38. A process as defined in claim 34 wherein said hydrocracking conditions are correlated so as to maintain a hydrogen consumption in the hydrocracking step of between about 300 and 1,500 s.c.cE. per barrel of feed.

39. A process as defined in claim 34 wherein the unconverted oil boiling `above the gasoline range from said hydrocracking step is recycled at least in part to said hydrocraclning step.

40. A process as defined in claim 34 wherein the unconverted oil boiling above the gasoline range from said hydrocracking step is recycled at least in part to said nonhydrogenative cracking step.

References Cited in the file of this patent UNITED STATES PATENTS 2,838,582 Kassel et al June 10, 1958 2,870,226 Deanesly Jan. 20, 1959 2,885,346 Kearby et al. May 5, 1959 Attesting Officer UNITEDv STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,008,895 C November 14f 1961l Rowland C.. Hansford et alav It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

each occurrence,

Column 2, line 50, for "wheer" read m wher-e w, column 5 line 5, for "Vith" read with same column 5v line 44, for "or" read of --3 column 7, line .5*7 after "may" insert be line l3, for "beta-" read betacolumn 8l line 22TI for "CoC" read COO column lO, line 64q after "an" insert octane number of 98() CF1+3 ml. TEL)o columnQlZ, line 49, for "octance" read f octane line 6l for "oxide" read oxides -e'i column 13, line 7l, and column 17,' line 5, for "15'00':l

read l5OOO Signed and sealed this 17th day of April 1962.,

(SEAL) Attest:

ESTON G., JOHNSON DAVID I l LADD Commissioner of Patents 

9. A PROCESS FOR PRODUCING HIGH OCTANE GASOLINE FROM A VIRGIN GAS OIL CONTAMINATED WITH SULFUR COMPOUNDS, WHICH COMPRISES FIRST SUBJECTING SAID GAS OIL TO CATALYTIC CRACKING IN THE PRESENCE OF A SILICEOUS CRACKING CATALYST UNDER CONDITIONS OF CRACKING ADJUSTED TO PRODUCE A HIGH-OCTANE CRACKED GASOLINE, AND A RESIDUAL OIL BOILING BETWEEN ABOUT 400* AND 750*F., AND CONTAINING AT LEAST ABOUT 25% BY VOLUME OF ACID-SOLUBLE COMPONENTS, SUBJECTING SAID RESIDUAL OIL TO HYDROCRACKING IN THE PRESENCE OF ADDED HYDROGEN AND A HYDROCRACKING CATALYST, MAINTAINING HYDROCRACKING CONDITIONS INCLUDING TEMPERATURES BETWEEN ABOUT 750* AND 1,000*F., PRESSURES BETWEEN ABOUT 500 AND 5,000 P.S.I.G., SPACE VELOCITIES BETWEEN ABOUT 0.5 AND 8.0, AND HYDROGEN RATIOS BETWEEN ABOUT 800 AND 15,000 S.C.F. PER BARREL OF FEED, THEREBY PRODUCING A LOW-SULFUR, AROMATIC-NAPHTHENIC GASOLINE FRACTION CONTAINING SUBSTANTIAL PROPORTIONS OF MONOCYCLIC NAPHTHENES BUT CONTAINING NOT MORE THAN ABOUT 50% BY VOLUME OF OPEN-CHAIN HYDROCARBONS, THEN, WITHOUT FURTHER DESULFURIZATION, SUBJECTING THE GASOLINE FROM SAID HYDROCRACKING TO A MILD REFORMING IN THE PRESENCE OF ADDED HYDROGEN AND A PLATINUM- 